In conventional practice, access to a vessel of the cardiovascular system of a patient may be obtained using a vascular entry sheath. Generally, a needle is used to puncture a blood vessel of entry (such as an artery), and a guidewire is passed through the needle to a desired location in the vessel. The needle is withdrawn and the guidewire is maintained in position in the vessel. Then a short sheath is advanced into the vessel over the guidewire to facilitate introduction of a diagnostic or therapeutic catheter. A catheter is advanced through the sheath, and the guidewire may then be removed. Once the distal end of the catheter is advanced to the target vessel, diagnostic or therapeutic procedures may be carried out. Depending on the type of catheter employed, fluid agents may be injected through the catheter for diagnostic or therapeutic purposes. However, if it is necessary or desirable to inject an x-ray contrast agent into a target vessel, a large caliber catheter must be advanced through the sheath to the target vessel, so as to provide for sufficiently high flow rates to displace blood with contrast agent. In most cases, the sheath itself may not serve as the conduit for delivery of contrast agent because conventional sheaths are usually quite short and are not adapted to selectively engage a vessel of the cardiovascular system. Furthermore, conventional sheaths have only a single end hole, and fluid injected therethrough in volumes sufficient for a contrast agent would likely flow from the end hole at such a velocity that tissue damage might occur. Consequently, a conventional sheath is used only to provide access to the vessel of entry, and a catheter is advanced through the sheath to reach a target vessel. If it is desired to deliver a fluid agent such as contrast fluid to a segment of the target vessel, it is generally necessary to employ a diagnostic catheter. If it is desired, after imaging of the target area, to employ another therapeutic or diagnostic device, the diagnostic catheter must first be removed, so that a second interventional device may be advanced to the target area.
Various catheters for distribution of fluid agents (sometimes referred to as infusion catheters) are known. For example, U.S. Pat. No. 5,021,044 of Sharkawy describes a vascular catheter having an inner lumen for receiving a guidewire and at least one concentrically disposed outer lumen for delivery of a fluid agent. The outer lumen is provided with a number of flow passageways to maintain a desired flow pattern to the target site, typically of about 0.1-1.5 cm.sup.3 /hour. U.S. Pat. No. 5,599,324 of McAlister et al. and U.S. Pat. No. 5,709,874 of Hanson et al. describe similar multi-lumen catheters. U.S. Pat. No. 5,380,307 of Chee et al. and U.S. Pat. No. 5,425,723 of Wang describe perfusion catheters that are designed to deliver a fluid agent through side holes uniformly along a perfusion portion of the catheter. These devices operate to deliver fluid to a target point within a vessel at low flow rates that are useful for introduction of pharmacological agents such as thrombolytic drugs, but are wholly insufficient for proper introduction of a contrast agent. Furthermore, these devices do not accommodate or facilitate the introduction of a second interventional device into the cardiovascular system of a patient.
U.S. Pat. No. 5,569,197 of Helmus et al. describes a hollow infusion guidewire over which a catheter may be introduced into a vessel. Preferably, the Helmus guidewire has an outer diameter that is comparable to that of a standard coronary guidewire, typically about 0.014 inch. It also has a plurality of openings or perforations in the sidewall near its distal end for dispersal of a drug therethrough. However, since it is sized to function as a guidewire too, it may only be used to disperse fluid at the target location at a very low rate, thereby limiting its use to the delivery of drugs only.
Many of the known infusion guidewires include complicated multi-lumenal structures and valve arrangements that are difficult and expensive to manufacture. Furthermore, these devices generally operate to deliver fluid agents to a target site at low flow rates that are wholly insufficient for use in delivering contrast media. Other devices that may be employed to deliver contrast media at an appropriate rate permit flow at a velocity that is likely to cause tissue damage. Thus, for example, U.S. Pat. No. 5,180,364 of Ginsburg describes a self-perfusing guiding catheter that is adapted for delivery of contrast media through a central lumen. The catheter includes a number of holes or slits that are provided with one-way valves so as to selectively permit fluid communication between the central lumen and the exterior of the device. When contrast media is injected through the central lumen, the valves close so that all of the contrast fluid is delivered out the end of the device. When no fluid is injected, the valves open to prevent the device from blocking blood flow within the vessel by permitting perfusing blood to flow into and through the catheter. After imaging of the target area is obtained, as by radiographic examination of the contrast media, a second catheter may be introduced through the central lumen and advanced to the target area. However, when the Ginsburg device is used to deliver a significant volume of contrast fluid in order to displace blood volume, the velocity of delivery of contrast fluid out the end hole may be so great that tissue damage may occur.
It would be desirable therefore if a vascular interventional device were developed that would be relatively simple and inexpensive to manufacture. It would also be desirable if such a device were developed that could be used to deliver fluid such as contrast media to a target area at a rate sufficient to displace blood so that a radiologic examination of the target area could provide useful information, but at a velocity that would minimize tissue damage. In addition, it would be desirable if such a device were developed that could be used to deliver fluid at an effective rate while a second interventional device was being used to diagnose or treat a condition.